James Dimon is no minnow.

The "London Whale" trading debacle that JP Morgan Chase suffered in 2012 may lead more shareholders at this spring's annual meeting to vote in favor of separating Dimon's roles as chairman and chief executive at the bank. But even $6bn or so in losses isn't likely to be enough to unseat Dimon, who is credited with steering JP Morgan successfully through the financial crisis.

Still, the argument for stripping even Dimon of one of his titles, and for similar change at other big banks like Goldman Sachs, is credible even absent the Whale.

A group of pension funds on Wednesday said they had filed a shareholder proposal calling for JP Morgan to name an independent chairman. A similar proposal last year received a 40% favorable vote.

While noting JP Morgan's Whale problem, the shareholder group also called out the bigger issue: the conflict that exists in having a combined chairman and chief executive, even absent a trading blowup. This revolves around the fact that the two jobs have very different objectives.

The chief executive is there to run the business. The chairman is there to represent the interests of shareholders. While those should usually be complementary, they can come into conflict, especially since the chief executive is the one providing the board with information.

At banks, this is a particular vulnerability. With much of a bank's balance sheet tied up in loans whose value is in many ways dependent on management's own view, additional checks are needed. That is all the more so given the systemic risk big banks continue to pose to the financial system.

In that case, a separation of power is needed, no matter how big a wake top executives cut.